Pitfall traps are used to sample litter inhabiting crickets, but some species are underestimated, because captured individuals escape from the trap. Here we suggest the substitution of aqueous detergent killing solution by formol-glicerin-alcohool solution, to increase sampling efficiency. We tested two hypotheses: (i) formol solution reduces the escape of crickets from the traps; (ii) formol solution is repellent. We arranged 80 traps in pairs of traps formol/detergent and detergent/detergent, 20 cm between traps within pairs, and 3 m between pairs. We collected 105 cricket individuals, being 29 adults, from nine species, in three taxonomic groups: Phalangopsinae, Trigonidiinae, and Brachytrupinae. Capture of both adults and nymphs was not affected by proximity of formol solution traps. In formol-detergent pairs, formol traps captured more adult individuals than detergent traps, but the number of nymphs did not differ. Therefore, formol was not repellent neither for adults nor nymphs. Traps with formol were more eficient, because they retained more adults than those with detergent, because of knock-down effect. Nymphs were not affected by the killing solution because their escape frequency is already low, due to their tiny size and reduced sclerotization. Tiny size implies short jumps, insuficient to escape. Reduced sclerotization implies greater permeability, so that once fallen into the trap, nymphs cannot escape any more.
Methodology; inventary; ecology; locomotion behavior
